Slip-control calender



Feb 17, 1931. Q MINTON I 1,793,114

SLIP CONTROL CALENDER Filed March 2'7. 1929 INYENTOR 'Qgc/ere Mi? 7 0 it? ATTORN Y Patented Feb. 17, 1931 UNITED STATES PATENT I OFFICE OGDEN MIN'ION, OF GREENWICH, CONNECTICUT, ASSIGNOR TO MINTON VACUUM DRYER CORPORATION, A. CORPORATION OF DELAWARE' SLIP-CONTROL CALENDEIR Application filed March 27, 1929. Serial No. 350,243.

Heretofore paper has always been calendered in a calender with rolls arranged one directly above the other with the bearings so designed that the weight of each roll is carried on the next lower roll. As a rule these rolls are made of chilled cast iron and vary in diameter from a few inches to as much as 30 inches or more and in length from a few feet to as much as 24 feet or more of calendering surface. In the manufacture of some grades of fine paper the calender rolls have a cotton or paper surface put on the rolls in the form of rings and pressed very tightly so that the surface is very hard. In some instances the calenders are arranged with the alternate rolls of chilled iron and rolls covered with cotton or paper. Various finishes are thus obtained.

In the process of calendering paper, a sheet of paper passes through the calender stack, entering betweenthe top and second rolls,

passes around the various rolls and out between the bottom and next to the bottom rolls. The rolls are normally driven through the 2 bottom roll and the rolls above this are driven by friction from the roll next below. This causes a slight amount of slip which tends to iron out, polish, burnish or grind the surface of the paper, imparting to it a smooth finish.

Inasmuch as the slip of the rolls affects the finish of the paper I have found it desirable to be able to control this slip in order to be able to alter the type of finish. Thus as the amount of slip or grinding is increased, ap-

parently the hydration of the sheet of paper is increased and thus the finish put on the paper by the calender stack is increased.

I find that this slip can readily be controlled by connecting each roll with some device which, at the will of the operator, may be caused to either partially drive the roll, or to exert a drag on it. By thus being able separately to influence the rotation of the rolls in either a positive or negative way the slip at each nip may be controlled at will. The simplest method of having this positive and negative control is to connect each roll with a small electric motor which will either drive it forward, or serve as a dynamo if a drag is to be put on the roll, and to connect each such motor with an appropriate rheostat whereby its action can be controlled.

This method of carrying out my invention is shown in the accompanying drawings, in which the end view of a calender stack is illustrated diagrammatically where each of the rolls above the bottom one is provided with an electric slip control.

In these drawings, I show a usual form of calender'stack comprising the frame members 10 and the eight rolls numbered 12 to 26. The bottom roll 12 is driven by a motor 28, and each of the rolls above are driven bypower derived from the bottom roll and transmitted to successive rolls by frictional engagement of the rolls. Each of the rolls above the bottom one has connected to it a motordynamo 30. Such a connection may be made in any desired way as by belt, chain drive or gearing device. For the purposes of illustration the motor-dynamos 30 are here shown as direct current motors each of which is supplied with a field winding 32 for speed control. These motors are here shown as connected in multiple with the bus bars 34 and 36 fed by a generator 38. The generator 88 is shown as provided with a field winding 40 connected to the exciter buses 42 and 44 which are supplied with exciting current from any suitable source by feeders 50 and 52, and to which the motor field windings 32 are con- 1 nected each through a rheostat 46. The adjustment of the various elements should be such that under normal operating conditions the motor-dynamos 30 will approximately float on buses 34 and 36 and by varying the settings of rheostats 46 can be made either to take power from or deliver power to these buses. If desired, ammeters and voltmeters may be supplied as indicated in the connection between the motor-dynamos 30 and bus bars 34 and 36. 7

When the calender stack is in operation, the paper maker, by adjusting the rheostats 46, can give a positive or negative torque to each of the rolls 14 to 26 and thus can readily cause more or less slip between the rolls 'at any nip and thereby gain an additional control over the calendering of the paper.

This is very advantageous, for each paper maker has different ideas regarding just how much finish a sheet of paper should have and whether this should be so-called eggshell finished or a finish of high polish. 'Heretofore the paper maker has been unable to control the amount of slip between the calender rolls, and this invention now makes it possible for him, by adjusting the positive or negative torque on the rolls to gain an additional control over the calendering operation and thus enabling him to produce difi'erent types of finish from those that now can be made.

It is to be understood that my invention is not to be limited to the apparatus shown and described for the purpose of illustration, but that modifications thereof fall withv in its scope. For instance,'other means than motor-dynamos may be employed to regu late the slip of the rolls and if motor-dynamos are used they may be of either direct or alternating current type. In the latter event, generator 38 would be replaced by an alternator. The scope of my invention is to be measured by the appended claims viewed in the light of the prior art.

What I claim is:

1. In a paper machine having a driven roll and additional rolls adapted to be rotated by power derived from said driven roll, "control means for each of such addiq tional rolls comprising an electric motordynamo connected with each such rolls and means whereby each such motor-dynamo may be used to give either a positive or negative torque to the roll with which it is connected.

2. In a calender having a driven roll and additional rolls adapted to be rotated by power derived from the driven roll, slip controls for such additional rolls comprising a series of motor-dynamos connected separately to such additional rolls, bus-bars to which such motor-dynamos are connected, and means whereby said motor-dynamos' may be individually caused either to draw power from, or deliver power to such bus-bars, whereby the amount of slip between adjacent rolls may be controlled.

3. A paper machine comprising a driven roll, additional rolls adapted. to be rotated by power derived from said driven roll, and means to impart either positive or negative tofi ue individually to each of said additional ro s.

4. In a paper machine having a driven roll and, additional rolls adapted to be rotated by power derived from said driven roll,

additional rolls adapted to be rotated by power derived from the driven roll, slip controls for such additional rolls comprising a series of direct current motor-dynamos connected separately to such additional rolls,

bus-bars to which such motor-dynamos are control means for each of such additional 

